Semiconductor methods and devices

ABSTRACT

In some embodiments, a method of a semiconductor process includes conformally forming a spacer layer over a plurality of mandrels that are disposed over a mask layer, portions of the spacer layer disposed over opposing sidewalls of adjacent ones of the plurality of mandrels defining trenches therebetween, filling the trenches with a dummy material, and removing first portions of the dummy material in the trenches, thereby forming a plurality of openings in the dummy material. The method further includes filling the plurality of openings with a first material, removing a remaining portion of the dummy material in the trenches, and removing the plurality of mandrels after the removing the dummy material.

PRIORITY CLAIM AND CROSS-REFERENCE

This patent application is a continuation of U.S. patent applicationSer. No. 15/867,052, filed on Jan. 10, 2018, and entitled “SemiconductorMethods and Devices,” which is a continuation of U.S. patent applicationSer. No. 15/363,928, filed on Nov. 29, 2016, and entitled “SemiconductorMethods and Devices,” now U.S. Pat. No. 9,881,794, issued on Jan. 30,2018, which applications are hereby incorporated by reference herein asif reproduced in their entireties.

BACKGROUND

The semiconductor industry has experienced rapid growth due to ongoingimprovements in the integration density of a variety of electroniccomponents (e.g., transistors, diodes, resistors, capacitors, etc.). Forthe most part, improvement in integration density has resulted fromiterative reduction of minimum feature size, which allows morecomponents to be integrated into a given area.

As feature size continues to shrink in advanced semiconductormanufacturing process, conventional photolithography may not provideenough resolution for the desired pitch sizes. Multiple-patterningtechniques, such as self-aligned double-patterning (SADP) andself-aligned quadruple patterning (SAQP), may be used to pattern masklayers with small pitch sizes. The mask layer patterns defined bymultiple-patterning may need to be cut, e.g., when the patterned masklayer are used to form conductive features in subsequent processing. Cutmasks are used to form the cut patterns. Challenges exist in theformation of cut masks. There is a need in the art for improved methodsof forming cut masks.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of a semiconductor device, inaccordance with some embodiments.

FIG. 2 illustrates a cross-sectional view of another semiconductordevice, in accordance with some embodiments.

FIGS. 3-18 illustrate cross-sectional views of a semiconductor device atvarious stages of a semiconductor process, in accordance with anembodiment.

FIGS. 19-34 illustrate cross-sectional views of a semiconductor deviceat various stages of a semiconductor process, in accordance with anotherembodiment.

FIGS. 35-37 illustrates perspective views of a semiconductor device atvarious stages of a semiconductor process, in accordance with yetanother embodiment.

FIG. 38 illustrates a flow diagram of a semiconductor process, inaccordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments discussed herein relate to semiconductor processing, and inparticular, forming mask layers used for patterning (e.g., generatingcut patterns) in advanced semiconductor process nodes (e.g., 24 nm, 14nm, 10 nm, 7 nm, or beyond).

FIG. 1 illustrates a cross-sectional view of a semiconductor device 100at a certain stage of a semiconductor process, in accordance with someembodiments. As illustrated by FIG. 1, semiconductor device 100 includesan etch stop layer (ESL) 610 over one or more semiconductor layers 710,a dielectric layer 510 (e.g., a low-K dielectric layer 510) over ESL610, and three mask layers (e.g., hard mask layers 210, 310 and 410)formed successively over dielectric layer 510. A mandrel layer 115 isformed over hard mask layer 210.

The one or more semiconductor layers 710 may be or include asemiconductor substrate (also referred to as a substrate). The substratemay comprise a crystalline silicon substrate (e.g., wafer), althoughother suitable elemental semiconductor, such as a suitable compoundsemiconductor (e.g., gallium arsenide, silicon carbide, indium arsenide,indium phosphide, or the like), or a suitable alloy semiconductor (e.g.,silicon germanium carbide, gallium arsenic phosphide, or gallium indiumphosphide), or the like, may also be used. Further, the substrate mayinclude an epitaxial layer (epi-layer), may be strained for performanceenhancement, and/or may include a silicon-on-insulator (SOI) structure.Electrical devices, such as active devices (e.g., transistors) and/orinactive devices (e.g., resistors, capacitors, diodes, and the like) maybe formed in or on the substrate. In addition, the one or moresemiconductor layers 710 may include metal layers over the semiconductorsubstrate and the electrical devices, the metal layers may compriseinterconnect structures (e.g., electrically conductive lines and/orvias) that connect the electrical devices to implement certain functionsin accordance with the desired design. The processing disclosed in thepresent disclosure may be used to form conductive features (e.g.,conductive lines and/or vias) that connect to the electrical devicesand/or interconnect structures in the one or more semiconductor layers710, as an example. As another example, the one or more semiconductorlayers 710 may include semiconductor fin structures (e.g., finstructures of fin field-effect transistors (FinFETs)) formed in aprevious patterning process, and the processing disclosed in the presentdisclosure may be used to form cut patterns for the fin structures.

ESL 610 is formed of a material that has a high etching selectivityrelative to the overlying dielectric layer 510, and hence ESL 610 may beused to stop the etching of dielectric layer 510. ESL 610 may includesilicon carbide (SiC), silicon nitride (SiN), silicon oxynitride (SiON),silicon carbon-nitride (SiCN), or the like. Dielectric layer 510 mayinclude silicon oxide, silicon nitride, low-K dielectric material havinga dielectric constant (k-value) lower than about 3.0, about 2.5, or evenlower, or other suitable material.

Hard mask layer 210 comprises SiO, SiN, or a metal oxide such as TiO,ZrO, ZrTiO, in some embodiments, and may have a thickness ranging fromabout 5 nm to about 22 nm. Hard mask layer 310 comprises TiN or a metaloxide such as TiO, ZrO, ZrTiO, as examples, and may have a thicknessranging from about 5 nm to about 22 nm. Hard mask layer 410 comprisesSiO or SiN, and has a thickness ranging from about 5 nm to about 22 nm,in an exemplary embodiment.

Mandrel layer 115 includes silicon such as amorphous-silicon, and may beabout 50 nm thick, as an example. Mandrel layer 115 may include SiC orSiOC, and may be formed by a spin-on deposition process or a chemicalvapor deposition (CVD) deposition process. as another example. Mandrellayer 115 is patterned to form mandrels 110 in FIG. 3 which will be usedin subsequent processing to pattern other underlying layers (e.g., hardmask layers 210), in some embodiments.

FIG. 2 illustrates the cross-sectional view of another semiconductordevice 200 at a certain stage of a semiconductor process, in accordancewith another embodiment. The semiconductor device 200 in FIG. 2 issimilar to the semiconductor device 100 in FIG. 1, but with a hard masklayer 103 and a mandrel layer 113 formed successively over mandrel layer115. Hard mask layer 103 comprises silicon oxide (SiO), SiN, or a metaloxide, such as TiO, ZrO, ZrTiO, in some embodiments. A thickness of hardmask layer 103 may range from about 5 nm to about 22 nm. Mandrel layer113 may have a similar composition and dimension as mandrel layer 115,although other compositions and dimensions are also possible. Materialsand dimensions of other layers of semiconductor device 200 in FIG. 2 maybe similar to that of FIG. 1, and, as such, details are not repeated.Skilled artisans will readily appreciate variations and modifications tothe semiconductor devices of FIG. 1 and FIG. 2. For example, the numberof hard mask layers may be increased or decreased in accordance withfactors such as the desired design and process technology. As anexample, hard mask layer 210 and hard mask layer 410 in FIGS. 1 and 2may be omitted.

FIGS. 3-18 illustrate cross-sectional views of a semiconductor device100 at various stages of a semiconductor process (e.g., a patterningprocess), in accordance with an embodiment. In FIGS. 3-18, a figurenumber with a “B” (e.g., FIG. 9B) represents a top view of thesemiconductor device, and a figure number with an “A” (e.g., FIG. 9A)represents a cross-sectional view along line A-A of the correspondingtop view figure (e.g., FIG. 9B). A figure number (e.g., FIG. 3) without“A” or “B” illustrates the same cross-sectional view as FIG. 9A. Notethat for simplicity, not all layers of the semiconductor device 100 areillustrated in all Figures. For example, FIG. 3 only shows mandrels 110and hard mask layer 210, and other layers underlying hard mask layer 210are not shown. One of ordinary skill, upon reading the presentdisclosure, would readily recognize layers of semiconductor device 100that are omitted from the figures.

Referring to FIG. 3, a plurality of mandrels 110 are formed over hardmask layer 210 by, e.g., patterning a mandrel layer such as mandrellayer 115 in FIG. 1 or mandrel layer 115 in FIG. 2. For example, mandrellayer 115 in FIG. 1 may be patterned by a photolithography and etchingprocess to form mandrels 110 in FIG. 3. The patterning of mandrel layer115 may use a dry etch process with an etch process gas includingfluorine (F) or chlorine (Cl). In an exemplary embodiment in whichmandrel layer 115 comprises silicon, mandrel layer 115 is etched usingan etch process gas comprising Cl. In particular embodiments, the etchprocess gas is a combination of gases and may include Cl₂, HBr, N₂, CH₄,He, and Ar. In another embodiment in which mandrel layer 115 comprisescarbon, mandrel layer 115 is etched using an etch process gas comprisingF, H, or O. In particular embodiments, the etch process gas may be acombination of gases including N₂, H₂, NH₃, and Ar. An anisotropicplasma etch process may be used to pattern mandrel layer 115. A width Wof mandrels 110 may depend on the semiconductor process nodes used. Forexample, W is about 22 nm for a particular process node, and is about 14nm for another more advanced process node. A height H of mandrel 110 maybe about 50 nm, as an example, although other dimensions are alsopossible. While FIG. 3 shows only four mandrels 110, it is to beunderstood that more or less than four mandrels may be formed, dependingon the design of the semiconductor device.

The embodiments of the etch process gases described herein are merelyexamples and are not intended to be limiting. Other suitable etchingprocess gases comprising gas(es) different from the embodimentsdescribed herein are also possible, and are fully intended to beincluded within the scope of the disclosure.

As another example, mandrel layer 115 in FIG. 1 may be patterned by anSADP process to form mandrels 110 illustrated in FIG. 3. An SADP processmay be used to form patterns with dimensions smaller than what theconventional photolithography process could achieve. In the SADPprocess, another mandrel layer (not shown) above mandrel layer 115 inFIG. 1 is first patterned by a photolithography and etching process toform a plurality of mandrels (not shown) that are disposed on a masklayer (not shown) between the another mandrel layer and mandrel layer115. Next, a spacer layer (not shown) is conformally deposited over theplurality of mandrels and the mask layer. An etching process, such as ananisotropic etching process, is performed to remove portions of thespacer layer disposed on the top surface of the mask layer and the topsurfaces of the plurality of mandrels without substantially removing thespacer layer disposed on sidewalls of the plurality of mandrels. Asubsequent selective etching process removes the plurality of mandrels.The remaining portions of the spacer layer, which were disposed onsidewalls of the plurality of mandrels before the plurality of mandrelswere selectively removed, form a plurality of spacers (not shown) withsmall pitches (e.g., half of the critical dimension of the semiconductorprocess node). The patterns of the spacers are transferred to the masklayer overlying mandrel layer 115 (e.g., by an anisotropic etchingprocess), and the patterned mask layer is used to pattern mandrel layer115 of FIG. 1 to form mandrels 110 in FIG. 3.

In another embodiment, mandrels 110 in FIG. 3 are formed by performingan SAQP process to pattern mandrel layer 115 in FIG. 2. An SAQP processmay be implemented by performing the processing in an SADP processtwice. For example, for semiconductor device 200 illustrated in FIG. 2,a first SADP process, similar to the SADP process described above forpatterning mandrel layer 115 in FIG. 1, is performed to pattern mandrellayer 113 in FIG. 2 to form a plurality mandrels (not shown) over masklayer 103. The plurality of mandrels are used in a second SADP processperformed to pattern mandrel layer 115 of FIG. 2, thereby resulting inmandrels 110 shown in FIG. 3. An SAQP process may produce patterns(e.g., mandrels 110) with finer pitches than that of an SADP process.

Referring to FIG. 4, a spacer layer 121 is formed over mandrels 110 andhard mask layer 210. Spacer layer 121 comprises SiO, SiN, or a metaloxide (e.g., TiO), in some embodiments. In the illustrated embodiment,spacer layer 121 is conformal, and is formed by a conformal depositionmethod such as ALD. Other suitable deposition methods, such as chemicalvapor deposition (CVD), may also be used. The thickness of spacer layer121 ranges from about 5 nm to about 22 nm, in an embodiment, althoughother dimensions are also possible. In another embodiment, the thicknessof spacer layer 121 is determined by the semiconductor process nodesused. For example, spacer layer 121 is about 22 nm thick for onesemiconductor process node, and is about 14 nm thick for another moreadvanced semiconductor process node. As illustrated in FIG. 4, trenches123′ (e.g., recesses, openings, or empty spaces) are formed betweenadjacent mandrels 110 after the deposition of spacer layer 121.

Next, referring to FIG. 5, spacer layer 121 is recessed to expose theupper surfaces of mandrels 110 and the upper surface of hard mask layer210 using, e.g., a dry etch process such as an anisotropic plasma etch.In embodiments in which spacer layer 121 comprises SiO or SiN, spacerlayer 121 is etched by an etch process gas comprising F. In particularembodiments, an etch process gas may be a combination of gases includingCF₄, CHF₃, CH₃F, N₂, CH₄, O₂, He, and Ar. In embodiments in which spacerlayer 121 comprises an metal oxide (e.g., TiO), spacer layer 121 isetched by an etch process gas comprising Cl. In particular embodiments,an etch process gas may be a combination of gases including Cl₂, HBr,CH₄, N₂, H₂, He, Ar, and O₂. The anisotropic plasma etch process removesportions of spacer layer 121 disposed over upper surfaces of mandrels110 and the upper surface of hard mask layer 210, without substantiallyremoving the remaining portions of spacer layers 121 over sidewalls ofmandrels 110, as illustrated in FIG. 5. The remaining portions of spacerlayer 121 on sidewalls of mandrels 110 are also referred to as spacers120. The empty spaces between adjacent spacers 120 disposed on opposingsidewalls of adjacent mandrels 110 are referred to as trenches 123.

Referring now to FIG. 6, a dummy material 131 (also referred to as asacrificial material) is formed over spacers 120, mandrels 110 and hardmask layer 210, and fills trenches 123 (illustrated FIG. 5). Theportions of dummy material 131 inside trenches 123 are referred to asdummy plugs, portions of which will be replaced by another material insubsequent processing. The dummy material 131 comprises a suitabledielectric material, such as spin-on glass (SOG) (e.g., SiOC), spin-ondielectric (SOD) (e.g., SiO), or spin-on metal oxide (SOM) (e.g., TiO),and are deposited using a spin-on deposition process in someembodiments. In other embodiments, dummy material 131 comprises aflowable oxide (e.g., SiO) that is deposited using a flowable chemicalvapor deposition (FCVD) process. Appropriate curing process(es) mayfollow the deposition process to cure the deposited dummy material 131.

Different regions of the wafer that comprise semiconductor device 100may have different pattern densities (e.g., densities of mandrels,trenches, etc.). This difference in pattern densities may cause dummymaterial 131 to have different thicknesses over different regions of thewafer (e.g., due to different amount of dummy material 131 the trenches123 may hold in different regions of the wafer), thereby resulting in aloading effect. A planarization process, such as a chemical mechanicalplanarization (CMP) process, may be performed to planarize the uppersurface of dummy material 131. In another embodiment, the wafer has asubstantially uniform pattern density, therefore there may be little orno loading effect, in which case the planarization process may beomitted.

However, by utilizing the materials disclosed above for dummy material131, the loading effect may be effectively reduced or eliminated by theCMP process in the presently disclosed method. For example, dummymaterial 131, once cured, is hard enough and responds well to the CMPprocess (e.g., yielding a substantially planar upper surface after theCMP process). In contrast, a conventional processing may use spin-oncarbon (SOC) to fill trenches 123. Since SOC is relatively soft, the CMPprocess is not effective in planarizing an uneven upper surface of SOC,thus the conventional processing may not be effective in handling theloading effect.

Referring to FIG. 7, top portions of dummy material 131 are removed toexpose upper surfaces of mandrels 110 and upper surfaces of spacers 120.The remaining portions of dummy material 131 inside trenches 123 (seeFIG. 5) are also referred to as dummy plugs 130. An etch back processsuch as a dry etch process may be performed to remove the top portionsof dummy material 131, using an etch process gas including F or Cl. Inan exemplary embodiment in which dummy material 131 comprises SOG (e.g.,SiOC) or SOD (e.g., SiO), dummy material 131 is etched using an etchprocess gas comprising F. In particular embodiments, SOG is etched usingan etch process gas including CH₃F, C₄F₆, O₂, CF₄, He, and Ar. Inanother embodiment in which dummy material 131 comprises SOM (e.g.,TiO), dummy material 131 is etched using an etch process gas comprisingCl. In particular embodiments, an etch process gas may be a combinationof gases including Cl₂, HBr, CH₄, N₂, He, and Ar. Besides the etch backprocess disclosed above, other suitable processes, such as CMP, may alsobe used to remove the top portions of dummy material 131. After theremoval of the top portions of dummy material 131, upper surfaces ofmandrels 110, upper surfaces of dummy plugs 130, and upper surfaces ofspacers 120 are substantially level with each other, as illustrated inFIG. 7.

FIGS. 8-11B illustrate processing steps to remove dummy plugs 130 atfirst locations (e.g., locations exposed by opening 143 in FIG. 9A, orpatterns P1, P2 and P3 in FIG. 9B). In FIG. 8, a first mask layer 140,e.g., a spin-on carbon (SOC) layer comprising carbon (C), and a secondmask layer 150, e.g., an SOG layer comprising SiOC, are successivelyformed over the structure shown in FIG. 7 using suitable formationmethod such as a spin-on deposition process. In an exemplary embodimentin which the first mask layer 140 is an SOC layer and the second masklayer 150 is an SOG layer, a thickness of SOC layer 140 is in a rangefrom about 40 nm to about 200 nm, and a thickness of SOG layer 150 is ina range from about 10 nm to about 40 nm. Next, a photo resist (PR) 160is formed over the second mask layer 150 and patterned by, e.g., alithography process. The patterned PR 160 has an opening 143 with alength X. In some embodiments, length X is about 1 time to about 3 timesthe thickness of spacers 120, where the thickness of spacers 120 (alsoreferred to as thickness of spacer layer 121) is measured in a directionperpendicular to the sidewalls of mandrels 110.

In FIG. 9A, the pattern (e.g., opening 143) of PR 160 is transferred tothe first mask layer 140 (e.g., an SOC layer) and the second mask layer150 (e.g., an SOG layer) by suitable etching processes, e.g.,anisotropic plasma etch processes, and PR 160 is removed by, e.g., anashing process or a stripping process. In some embodiments in which thesecond mask layer 150 is an SOG layer, the second mask layer 150 isetched by a plasma process using an etch process gas including F. Anetch process gas similar to the etch process gas used for the removal ofthe top portions of dummy material 131 comprising SOG (described withreference to FIG. 7) may be used. Additionally, in some embodiments inwhich the first mask layer 140 is an SOC layer, the first mask layer 140is etched by a plasma process using an etch process gas including H₂,N₂, O₂, NH₃, He, and Ar. After first mask layer 140 and second masklayer 150 are etched, opening 143 extends into second mask layer 150 andfirst mask layer 140, and exposes portions of dummy plugs 130 within theopening 143.

FIG. 9B illustrates the top view of the structure shown in FIG. 9A. Asnoted above, FIG. 9A corresponds to the cross-sectional view of FIG. 9Balong line A-A. Three patterns (e.g., openings) P1, P2 and P3 areillustrated in FIG. 9B, with pattern P2 corresponding to opening 143shown in FIG. 9A. In the top view, each pattern has the length X (alsoshown in FIG. 8) and a width Y. While each pattern (e.g., P1, P2 or P3)may have a different length X within the range described above, allpatterns (e.g., P1, P2 and P3) may have a same width Y. The width Y mayrange from about 5 nm to about 50 nm, e.g., 20 nm. In accordance withembodiments of the present disclosure, width Y is equal to the criticaldimension (CD) of the semiconductor process node used in fabricatingsemiconductor device 100. Using the same width Y for all patterns allowsfor the use of a conformal deposition process such as ALD to fillopenings 133 (see FIGS. 11A, 11B and 12) and to achieve a planar uppersurface for cut material 170 (see FIG. 12) after the ALD deposition insubsequent processing, as will be described in more detail hereinafter.

Note that patterns P1, P2 and P3 may not be formed at the same time(e.g., in a same processing step or using a same photolithography step).For example, the distance between P2 and P1, and the distance between P2and P3, may be too small for the resolution of photolithography, thusall three patterns P1, P2 and P3 could not be formed at the same timeusing one photolithography process. Instead, pattern P2 may be formed inone photolithography process, and patterns P1 and P3 may be formed inanother photolithography process. For example, processing stepsillustrated in FIGS. 8-11B may be performed for a first iteration togenerate pattern P2 and to remove dummy plugs 130 exposed by pattern P2.Then, the processing steps illustrated in FIGS. 8-11B may be performedfor a second iteration to generate patterns P1 and P3 and to removedummy plugs 130 exposed by patterns P1 and P3. Details regarding theremoval of dummy plugs 130 exposed by the patterns (e.g., P1, P2, or P3)are described below with reference to FIGS. 10, 11A and 11B. AlthoughFIG. 9B shows three patterns (e.g., P1, P2 and P3), skilled artisanswill appreciate that other numbers of patterns and other numbers ofiterations are possible, and the pattern(s) generated in each iterationmay be adjusted based on, e.g., desired design.

Referring to FIG. 10, second mask layer 150 is removed fromsemiconductor device 100 (e.g., by an etching process or a CMP process),and an etching process is performed to remove portions of dummy plugs130 exposed by opening 143 (e.g., see also pattern P2 in FIG. 9B), thusone or more openings 133 are formed at locations where the removedportions of dummy plugs 130 used to be. In some embodiments, dummy plugs130 exposed by opening 143 are removed by a dry etch process (e.g., aplasma process) using an etch process gas including Cl or F. In anexemplary embodiment in which dummy plugs 130 comprise SOG (e.g., SiOC)or SOD (e.g., SiO), dummy plugs 130 are etched using an etch process gascomprising F. In another embodiment in which dummy plugs 130 compriseSOM (e.g., TiO), dummy plugs 130 are etched using an etch process gascomprising Cl. In the illustrated embodiments, the etch process gas hasa high selectivity of dummy plugs 130 to spacers 120 (e.g., selectivityof dummy plugs 130 to spacers 120 is greater than 50), thus the etchprocess gas removes dummy plugs 130 exposed by opening 143 withoutsubstantially attacking spacers 120.

Referring now to FIGS. 11A and 11B, first mask layer 140 is removed byan etching process. A dry etching process using an etch process gasincluding H₂, N₂, or O₂, may be used to remove first mask layer 140(e.g., an SOC layer). FIG. 11B illustrates the corresponding top viewfor FIG. 11A. Note that only the portions of dummy plugs 130 exposed byopening 143 (e.g., pattern P2) are removed in FIG. 10, thus openings 133are illustrated as small rectangles/squares within the remainingportions of dummy plugs 130. Although openings 133 are illustrated asrectangles or squares in FIG. 11B, the shape of openings 133 may not beperfect rectangles or squares, and openings 133 may have other shapes.In addition, since openings 133 expose the underlying hard mask layer210 (see FIG. 11A), hard mask layer 210 is visible inside openings 133,as illustrated in the top view of FIG. 11B.

Note that all openings 133 in FIG. 11B may not be formed in a sameprocessing step or iteration, as discussed above with reference to FIG.9B. For example, openings 133 disposed on line A-A are formed in a firstiteration of processing using pattern P2 (see FIG. 9B), where eachiteration follows processing steps illustrated in FIGS. 8-11B. Then, inanother iteration, other openings 133 (e.g., openings not on line A-A)are formed using patterns P1 and P3 (see FIG. 9B).

Next, referring to FIG. 12, a cut material 170 (also referred to as afirst material) is formed over mandrels 110, spacers 120, (the remainingportions of) dummy plugs 130, and hard mask layer 210. Cut material 170also fills openings 133 generated by the dummy plug removal processdescribed above. Cut material 170 includes SiO, SiN, a metal oxide suchas TiO, combinations thereof, or the like, in an exemplary embodiment. Aconformal deposition process, such as an ALD process, is used toconformally deposit cut material 170 and to fill openings 133 with cutmaterial 170, in the illustrated embodiment. Recall that during thegeneration of patterns P1, P2 and P3 (see FIG. 9B), the widths Y of allpatterns have a small dimension and may be the same, which is thecritical dimension of the semiconductor processing node. Therefore, ALDdeposition is able to fill opening 133 and achieve a substantiallyplanar upper surface for cut material 170, as discussed below.

Using ALD to fill openings 133 provides several advantages. Since ALDforms a conformal layer, and since upper surfaces of mandrels 110, uppersurfaces of spacers 120 and upper surfaces of dummy plugs 130 are levelwith each other, the conformally formed cut material 170 also has aplanar upper surface over the upper surfaces of mandrels 110, uppersurfaces of spacers 120, and upper surfaces of dummy plugs 130, with asmall dip (not separately illustrated due to its small nature) in theplanarity of the cut material 170 occurring over openings 133. As anexample, for openings 133 with a pitch of 40 nm (e.g., measured along adirection perpendicular to line A-A in FIG. 11B), the size of opening133 (e.g., measured along the direction perpendicular to line A-A inFIG. 11B) may be 20 nm, and cut material 170 with a thickness of about15 nm may be used to fill opening 133. As another example, for openings133 with a pitch of 28 nm, the size of opening 133 may be 14 nm, and cutmaterial 170 with a thickness of about 10.5 nm may be used to fillopening 133. After openings 133 are filled with cut material 170 usingALD, cut material 170 may have a planar surface except for a small dipthat has a depth of about 50 nm. By having a surface as planar as this,the loading effect problem associated with conventional processing isavoided by using ALD deposition for cut material 170, and noplanarization of cut material 170 is needed after the ALD deposition. Byusing dummy material 131 and cut material 170 in the processing, thereis no longer a need for an SOC layer beneath the deposited cut material170, which relaxes the requirement for a low temperature (e.g., lessthan about 200° C.) deposition method. This improvement, together withthe ALD deposition method used, offers a wider selection of materialsfor cut material 170, which was not available previously with theconventional method (e.g., using SOC layer beneath cut material 170).

Next, referring to FIG. 13A, top portions of cut material 170 areremoved to expose mandrels 110, spacers 120 and dummy plugs 130. The cutmaterial 170 removal process is controlled to stop at the upper surfacesof spacers 120. A dry etching process using an etch process gasincluding Cl or F may be used. In an exemplary embodiment in which cutmaterial 170 comprises SiO or SiN, cut material 170 is etched using anetch process gas comprising F. In another embodiment in which cutmaterial 170 comprises a metal oxide (e.g., TiO), cut material 170 isetched using an etch process gas comprising Cl. The etch process gas maybe the same as the etch process gas used for the removal of the spacerlayer 121 comprising the same material, as described with reference toFIG. 5. In some embodiments, the etch process gas has an etchingselectivity of cut material 170 to spacers 120 that is more than 10.FIG. 13B illustrates the corresponding top view of FIG. 13A afterremoval of the top portions of cut material 170. As illustrated in FIG.13B, portions of dummy plugs 130 at the first locations (e.g., locationscorresponding to openings 133 in FIGS. 11A and 11B) are replaced by cutmaterial 170, thus cut material 170 is embedded into dummy plugs 130.

Referring now to FIGS. 14A and 14B, the remaining portions of dummyplugs 130 are removed, and the upper surface of hard mask layer 210 isexposed. A dry etching process using an etch process gas including Cl orF may be used. In an exemplary embodiment in which dummy plugs 130comprise SOG (e.g., SiOC) or SOD (e.g., SiO), dummy plugs 130 are etchedusing an etch process gas comprising F. In another embodiment in whichdummy plugs 130 comprise SOM (e.g., TiO), dummy plugs 130 are etchedusing an etch process gas comprising Cl. In the illustrated embodiments,the etch process gas has an etching selectivity of dummy plugs 130 tospacers 120 and cut material 170 that is more than 50. Therefore, theetch process gas removes the remaining portions of dummy plugs 130without substantially attacking spacers 120 and cut material 170.

Next, as illustrated in FIGS. 15A and 15B (which additionallyillustrates hard mask layer 310), mandrels 110 are removed. After theremoval of mandrels 110, spacers 120 and cut material 170 are left overhard mask layer 210. The pattern defined by spacers 120 and cut material170 will be transferred to hard mask layer 210 and used for etching theunderlying layers. In some embodiments, mandrels 110 are removed by adry etch process using an etch process gas including Cl or F. In anexemplary embodiment in which mandrels 110 comprise silicon, mandrels110 are etched using an etch process gas comprising Cl. In anotherembodiment in which mandrels 110 comprise carbon, mandrels 110 areetched using an etching gas comprising F, H, or O. The etch process hasa high selectivity of mandrels 110, for example, a selectivity ofmandrels 110 to spacers 120 and cut material 170 is more than 50.

Etch selectivity is advantageously used in some of the previousprocessing steps to remove a target material without attacking othermaterials, e.g., in the removal of dummy plugs 130 and the removal ofmandrels 110. Etch selectivity may be achieved by using differentmaterials for different layers of semiconductor device 100, and usingetch process gases that have different etch rates for differentmaterials. In an exemplary embodiment, spacer layer 121 (and spacers120) comprises a metal oxide (e.g., TiO) and is etched using an etchprocess gas comprising Cl, dummy material 131 (and dummy plugs 130)comprises SOG (e.g., SiOC) or SOD (e.g., SiO) and is etched using anetch process gas comprising F, cut material 170 comprises SiO or SiN andis etched using an etch process gas comprising F, and mandrels 110comprise silicon and are etched using an etch process gas comprising Cl.Other combinations of materials and etching process gases are possible,and are fully intended to be included within the scope of the presentdisclosure.

Next, in FIG. 16, the pattern defined by spacers 120 and cut material170 is transferred to hard mask layer 210. An anisotropic plasma etchmay be used to transfer the pattern to hard mask layer 210, althoughother suitable etching method may also be used. In some embodiments,hard mask layer 210 is etched using an etch process gas comprising F.

In FIG. 17, spacer layer 120 and cut material 170 are removed by asuitable method such as etching or grinding, and the pattern of hardmask layer 210 is transferred to hard mask layer 310 using a suitableprocess, e.g., an anisotropic plasma etch process. In some embodimentsin which hard mask layer 310 comprises TiN, hard mask layer 310 isetched using an etch process gas comprising Cl. FIG. 17 also illustrateshard mask layer 410 underlying hard mask layer 310, which hard masklayer 410 will be patterned in subsequent processing.

Next, in FIG. 18, hard mask layer 210 is removed by a suitable method(e.g., etching or grinding), and the pattern of hard mask layer 310 istransferred to hard mask layer 410 using, e.g., an anisotropic plasmaetch process. In some embodiments in which hard mask layer 410 comprisesSiO or SiN, hard mask layer 410 is etched using an etch process gascomprising F. Next, hard mask layer 310 and hard mask layer 410 are usedto pattern the underlying dielectric layer 510. An anisotropic etchingprocess, such as a plasma etch process, may be used to patterndielectric layer 510. After the patterning of dielectric layer 510,openings (e.g., openings 515 and 513) are formed in dielectric layer510.

The openings 515 and 513 might have different depths, which may beachieved by applying different amount of etching, e.g., in two or moreprocessing steps. For example, a first etch process may be performed toform openings 515 and upper portions (e.g., portions having a same depthin dielectric layer 510 as openings 515) of openings 513. Next, a masklayer (e.g., a PR, not shown) is formed over hard mask layer 310 tocover openings 515 while leaving openings 513 exposed, and subsequently,a second etch process is performed to extend (e.g., deepen) openings513, e.g., until ESL 610 is exposed, at which point a third etch processmay be used to remove portions of ESL 610 exposed by openings 513. Asillustrated in FIG. 18, opening 513 extends through dielectric layer 510and ESL 610, while opening 515 extends into dielectric layer 510 withoutextending through dielectric layer 510. Skilled artisans will appreciatethat the different openings may be used for forming different conductivefeatures (e.g., conductive lines, vias), and additional processing mayfollow the process illustrated in FIG. 18. For example, openings 515 and513 may be formed as part of a multi-step dual-damascene process.

FIGS. 19-34 illustrate cross-sectional views of a semiconductor device100 at various stages of fabrication, in accordance with anotherembodiment. The processing steps shown in FIGS. 19-34 are similar to theprocessing steps in FIGS. 3-18, with similar label numbers denotingsimilar elements, albeit with some differences between the embodiments.The processing steps shown in FIGS. 19-34 are briefly discussedhereinafter, with details of some of the differences between thedifferent embodiments highlighted. One of ordinary skill, upon readingthis disclosure, will fully understand the processing steps shown inFIGS. 19-34.

In FIG. 19, mandrels 110 are formed over hard mask layer 210. Spacerlayer 121 is deposited conformally over mandrels 110 in FIG. 20, withtrenches 123′ between adjacent mandrels 110 (also between portions ofspacer layer 121 disposed on opposing sidewalls of adjacent mandrels110). In FIG. 21, dummy material 131 is deposited over spacer layer 121and fills trenches 123′. Note that in FIG. 21, the deposition of dummymaterial 131 is performed without the etching of spacer layer 121. Inparticular, compared with the embodiment shown in FIGS. 3-18, theprocessing step shown in FIG. 5 is omitted in the current embodiment,thus upper surfaces of mandrel 110 are covered by spacer layer 121 inthe subsequent processing steps until the processing step shown in FIG.30A, where the top portions of spacer layer 121 are removed to exposemandrels 110.

In FIG. 22, the top portions of dummy material 131 is recessed by anetch back process similar to the discussion in FIG. 7, and the remainingportions of dummy material 131 in trenches 123′ (see FIG. 20) form aplurality of dummy plugs 130. After recessing the top portions of dummymaterial 131, a substantially planar upper surface is achieved betweenspacer layer 121 and dummy plugs 130. An optional planarization process(e.g., a CMP process) may be performed prior to the recessing of dummymaterial 131, similar to the discussion in FIG. 6.

FIGS. 23-26B illustrate processing steps used to remove portions ofdummy plugs 130 at first locations (e.g., locations of opening 133′ inFIG. 25). Details are similar to the processing shown in FIGS. 8-11B.Note that compared with openings 133 in FIG. 10, openings 133′ do notexpose hard mask layer 210 due to the existence of spacer layer 121 atthe bottom of openings 133′. Next, as illustrated in FIG. 27, cutmaterial 170 is deposited over spacer layer 121 and fills openings 133′left by the removal of (portions of) dummy plugs 130, similar to theprocessing of FIG. 12.

FIGS. 28A and 28B illustrate the structure in FIG. 27 after, e.g.,etching back of cut material 170. Subsequently, the remaining portionsof dummy plugs 130 are removed in FIG. 29. In FIGS. 30A and 30B, spacerlayer 121 is recessed to expose mandrels 110 and hard mask layer 210.Recessing of spacer layer 121 may be performed by a dry etch processusing an etch process gas including Cl or F. The dry etch gas may have ahigh etch selectivity of spacer layer 121 to hard mask layer 210 and cutmaterial 170, e.g., an etch selectivity of spacer layer 121 to hard masklayer 210 and cut material 170 is higher than 50. As a result, an uppersurface 170U of cut material 170 is higher (e.g., extending further awayfrom hard mask layer 210) than upper surfaces of mandrels 110 and theupper surface of the remaining portions (see label 122A and 122B) ofspacer layer 121 after the dry etch process. In other embodiments, thedry etch gas has a high etch selectivity of spacer layer 121 to hardmask layer 210, but has a similar etch selectivity as cut material 170,in which case after the dry etch process, the upper surface 170U of cutmaterial 170 may be level (not shown) with upper surfaces of mandrels110 and the upper surface of the remaining portions (see label 122A and122B) of spacer layer 121.

After the recessing of spacer layer 121, the remaining portions ofspacer layer 121 on sidewalls of mandrels 110 are referred to as spacers122 (e.g., spacers 122A and spacers 122B). Spacers 122A are similar tospacers 120 in FIG. 14A, e.g., spacers 122A on opposing sidewalls ofmandrels 110 are separate from each other, and there is no spacer layer121 between a first spacer 122A on a sidewall of a first mandrel 110 anda second spacer 122A on an opposing sidewall of a second mandrel 110. Incontrast, spacers 122B on opposing sidewalls of two adjacent mandrels110 are connected by a remaining portion of spacer layer 121 under cutmaterial 170. Therefore, spacers 122B on opposing sidewalls of twoadjacent mandrels 110 and the remaining portion of spacer layer 121under cut material 170 form a U-shaped structure comprising a samematerial (e.g., material used for forming spacer layer 121). TheU-shaped structure represents portions of spacer layer 121 that extendcontinuously from a first sidewall of a first mandrel 110 to an opposingsidewall of a second mandrel 110 adjacent the first mandrel.

Next, mandrels 110 are removed, as illustrated in FIGS. 31A and 31B. Thespacers 122 and cut material 170 defines a pattern which will be used topattern the underlying layers.

FIGS. 32 to 34 illustrate the transferring of the pattern defined byspacers 120 and cut material 170 to hard mask layers (e.g., hard masklayers 210, 310 and 410), and the patterning of dielectric layer 510,similar to the processing of FIGS. 16-18.

FIGS. 35-37 illustrates perspective views of a semiconductor device 300at various stages of processing, in accordance with another embodimentof the present disclosure. Semiconductor device 300 is similar tosemiconductor device 100, with similar label numbers denote similarelements. In particular, semiconductor device 300 in FIG. 35, FIG. 36,and FIG. 37 are at processing stages similar to the processing stagesillustrated in FIGS. 31A/31B, FIG. 33, and FIG. 34, respectively.However, differences exist between semiconductor device 300 andsemiconductor device 100. For example, compared with semiconductordevice 100 in FIGS. 31A/31B, semiconductor device 300 in FIG. 35 hasdifferent patterns defined by cut material 170 and spacer 122′.Additionally, while semiconductor device 100 illustrated in FIGS.31A/31B may have a planar top surface, spacers 122′ in FIG. 35 do nothave a planar upper surface.

FIG. 38 illustrates a flow chart of a semiconductor process 1000, inaccordance with some embodiments. It should be understood that theembodiment method shown in FIG. 38 is an example of many possibleembodiment methods. One of ordinary skill in the art would recognizemany variations, alternatives, and modifications. For example, varioussteps as illustrated in FIG. 38 may be added, removed, replaced,rearranged and repeated.

Referring to FIG. 38, at step 1010, a spacer layer is conformally formedover a plurality of mandrels that are disposed over a mask layer,portions of the spacer layer disposed over opposing sidewalls ofadjacent ones of the plurality of mandrels defining trenchestherebetween. At step 1020, the trenches are filled with a dummymaterial. At step 1030, first portions of the dummy material are removedin the trenches, thereby forming a plurality of openings in the dummymaterial. At step 1040, the plurality of openings is filled with a firstmaterial. At step 1050, a remaining portion of the dummy material isremoved in the trenches. At step 1060, the plurality of mandrels areremoved after the removing the dummy material.

Embodiments of the methods in the current disclosure have manyadvantages. For example, by using SOG, SOD or SOM as the dummy material131, better physical properties (e.g., hardness) are obtained, and CMPmay be used to achieve a planar upper surface, thus reducing or solvingthe loading effect problem. Additionally, by controlling the dimensionof width Y in the PR patterns (e.g., patterns P1, P2, P3 in FIG. 9B) tohave a fixed dimension (e.g., the critical dimension of the processnode), a conformal deposition method such as ALD may be used for formingcut material 170 and filling the openings (e.g., opening 133 in FIG. 10)created by the dummy plug removal process. The ALD method naturallyforms a planar upper surface, due to the underlying planar uppersurface, thus no planarization process is needed after the deposition ofcut material. In addition, the presently disclose methods allows a widerselection of materials for the cut material 170, which was notpreviously available.

In some embodiments, a method of a semiconductor process includesconformally forming a spacer layer over a plurality of mandrels that aredisposed over a mask layer, portions of the spacer layer disposed overopposing sidewalls of adjacent ones of the plurality of mandrelsdefining trenches therebetween, filling the trenches with a dummymaterial, and removing first portions of the dummy material in thetrenches, thereby forming a plurality of openings in the dummy material.The method further includes filling the plurality of openings with afirst material, removing a remaining portion of the dummy material inthe trenches, and removing the plurality of mandrels after the removingthe dummy material.

In other embodiments, a method of forming a mask pattern includesforming a plurality of mandrels over a mask layer, forming a pluralityof spacers over sidewalls of the plurality of mandrels, where spacers onopposing sidewalls of adjacent ones of the plurality of mandrels formtrenches in between, and filling the trenches with a sacrificialmaterial. The method further includes replacing a first portion of thesacrificial material with a first material, removing a remaining portionof the sacrificial material, removing the plurality of mandrels, andtransferring a first pattern from the spacers and the first material tothe mask layer.

In yet another embodiment, a method of semiconductor processing includesconformally forming a spacer layer over a plurality of mandrels disposedon a mask layer, depositing a sacrificial material over the spacer layerand the mask layer using at least in part spin-on deposition or flowablechemical vapor deposition, the sacrificial material comprising siliconoxide carbide, silicon oxide, or a metal oxide, the sacrificial materialfilling trenches between adjacent ones of the plurality of mandrels, andremoving top portions of the sacrificial material to expose an uppersurface of the spacer layer. The method also includes performing atleast one patterning and etch process to remove a first portion of thesacrificial material, thereby forming openings in the sacrificialmaterial. The performing at least one patterning and etch processincludes forming a first etch mask to expose the sacrificial material atfirst locations, the first etch mask having a first length and a firstwidth, and selectively removing the sacrificial material at the firstlocations after the forming the first etch mask. The method alsoincludes filling the openings using a first material. The filling theopenings includes depositing a first material over the spacer layer andthe mask layer using atomic layer deposition, the first materialcomprising silicon nitride, silicon oxide, or titanium oxide, andremoving top portions of the first material to expose an upper surfaceof a remaining portion of the sacrificial material. The method furtherincludes removing the remaining portion of the sacrificial material, andremoving the plurality of mandrels.

In an embodiment, a method includes conformally forming a spacer layerover a plurality of mandrels that are disposed over a mask layer,portions of the spacer layer disposed over opposing sidewalls ofadjacent ones of the plurality of mandrels defining trenchestherebetween; filling the trenches with a dummy material such that thespacer layer is interposed between the dummy material and the masklayer; removing first portions of the dummy material in the trenches,thereby forming a plurality of openings in the dummy material; fillingthe plurality of openings with a first material; removing remainingportions of the dummy material in the trenches; after removing theremaining portions of the dummy material, recessing the spacer layer toexpose the plurality of mandrels; and removing the plurality of mandrelsafter recessing the spacer layer.

In an embodiment, a method includes forming a plurality of mandrels overa mask layer; forming a plurality of spacers on sidewalls of theplurality of mandrels, where spacers on opposing sidewalls of adjacentones of the plurality of mandrels form trenches in between; filling thetrenches with a sacrificial material; replacing a first portion of thesacrificial material with a first material, the first material extendingfrom a first spacer on a first sidewall of a first mandrel to anopposing second spacer on a second sidewall of a second mandrel adjacentthe first mandrel; removing a remaining portion of the sacrificialmaterial; and removing the plurality of mandrels.

In an embodiment, a method includes conformally forming a spacer layerover a plurality of mandrels disposed on a mask layer; depositing asacrificial material over the spacer layer and over the mask layer, thesacrificial material filling trenches between adjacent ones of theplurality of mandrels; removing the sacrificial material from an uppersurface of the spacer layer; performing an etching process to remove afirst portion of the sacrificial material, thereby forming openings inthe sacrificial material, where performing the etching process includes:forming a first patterned mask over the sacrificial material and overthe spacer layer, the first patterned mask having a first etch patternwith a first length and a first width, the first etch pattern exposingthe first portion of the sacrificial material; and selectively removingthe first portion of the sacrificial material exposed by the first etchpattern of the first patterned mask. The method further includes fillingthe openings with a first material, where filling the openings includes:depositing the first material over the spacer layer, over the masklayer, and over a remaining portion of the sacrificial material; andremoving a top portion of the first material to expose the remainingportion of the sacrificial material, where after removing the topportion of the first material, an upper surface of a remaining portionof the first material is level with an upper surface of the remainingportion of the sacrificial material. The method further includesremoving the remaining portion of the sacrificial material; and removingthe plurality of mandrels.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a spacer layer overa plurality of mandrels that are disposed over a mask layer; afterforming the spacer layer, filling trenches between the plurality ofmandrels with a dummy material; removing first portions of the dummymaterial in the trenches, thereby forming a plurality of openings in thedummy material; filling the plurality of openings with a first material;removing remaining portions of the dummy material in the trenches; andafter removing the remaining portions of the dummy material, removingthe plurality of mandrels.
 2. The method of claim 1, wherein filling thetrenches comprises filling the trenches between the plurality ofmandrels with the dummy material such that the spacer layer isinterposed between the dummy material and the mask layer.
 3. The methodof claim 2, further comprising, after removing the remaining portions ofthe dummy material and before removing the plurality of mandrels,recessing the spacer layer to expose the plurality of mandrels.
 4. Themethod of claim 3, wherein recessing the spacer layer further exposesportions of the mask layer.
 5. The method of claim 3, wherein afterrecessing the spacer layer, an upper surface of the first materialextends further from the mask layer than an upper surface of the spacerlayer.
 6. The method of claim 1, wherein forming the spacer layercomprises performing a conformal deposition process to form the spacerlayer over the plurality of mandrels.
 7. The method of claim 1, whereinremoving the first portions of the dummy material comprises: forming apatterned mask layer over the spacer layer and over the dummy material;and selectively removing the dummy material exposed by a first patternof the patterned mask layer.
 8. The method of claim 7, wherein the firstpattern in the patterned mask layer has a first length and a firstwidth, the first width extending along a direction perpendicular to thefirst length, the first length and the first width being in a planeparallel to a major upper surface of the mask layer, wherein the firstwidth is a same as a critical dimension of a semiconductor process usedto form the first pattern.
 9. The method of claim 7, wherein selectivelyremoving the dummy material comprises performing an anisotropic etchprocess.
 10. The method of claim 9, wherein the anisotropic etch processuses an etching gas that is selective to the dummy material.
 11. Themethod of claim 1, wherein filling the plurality of openings comprisesperforming an atomic layer deposition process to fill the plurality ofopenings with the first material.
 12. A method comprising: forming aplurality of mandrels over a mask layer; forming a plurality of spacersalong sidewalls of the plurality of mandrels, wherein spacers onopposing sidewalls of adjacent mandrels define trenches in between;filling the trenches with a sacrificial material; replacing a firstportion of the sacrificial material with a first material, a width ofthe first material being a same as a width of the sacrificial material;removing a remaining portion of the sacrificial material; and removingthe plurality of mandrels.
 13. The method of claim 12, furthercomprising, after removing the remaining portion of the sacrificialmaterial and after removing the plurality of mandrels, transferring apattern defined by the spacers and the first material to the mask layer.14. The method of claim 12, wherein forming the plurality of spacerscomprises: depositing a conformal spacer layer over the plurality ofmandrels and over the mask layer; and performing an anisotropic etch toremove portions of the conformal spacer layer that are disposed over themask layer and over upper surfaces of the plurality of mandrels.
 15. Themethod of claim 12, wherein the sacrificial material is silicon oxidecarbide, silicon oxide, titanium oxide, or combinations thereof.
 16. Themethod of claim 12, wherein the replacing comprises: forming a firstetch mask over the plurality of spacers and over the sacrificialmaterial, the first etch mask having a first opening with a first lengthand a first width, the first opening exposing at least portions of thesacrificial material and portions of the plurality of spacers; andselectively removing the sacrificial material exposed by the firstopening of the first etch mask, thereby forming a first plurality ofopenings in the sacrificial material.
 17. The method of claim 16,wherein the replacing further comprises, after forming the firstplurality of openings: forming a second etch mask over the plurality ofspacers and over the sacrificial material, the second etch mask having asecond opening with a second length and a second width, wherein thesecond width is a same as the first width; selectively removing thesacrificial material exposed by the second opening of the second etchmask, thereby forming a second plurality of openings in the sacrificialmaterial; and filling the first plurality of openings and the secondplurality of openings with the first material.
 18. The method of claim17, wherein the first length and the second length are different.
 19. Amethod comprising: conformally forming a spacer layer over a pluralityof mandrels disposed on a mask layer; depositing a sacrificial materialover the spacer layer and over the mask layer, the sacrificial materialfilling trenches between adjacent ones of the plurality of mandrels;performing an etching process to remove a first portion of thesacrificial material, thereby forming openings in the sacrificialmaterial, wherein performing the etching process comprises: forming afirst patterned mask over the sacrificial material and over the spacerlayer, the first patterned mask exposing the first portion of thesacrificial material; and selectively removing the first portion of thesacrificial material exposed by the first patterned mask; filling theopenings with a first material; removing a remaining portion of thesacrificial material; and removing the plurality of mandrels.
 20. Themethod of claim 19, wherein filling the openings comprises: depositingthe first material over the spacer layer, over the mask layer, and overa remaining portion of the sacrificial material; and removing a topportion of the first material to expose the remaining portion of thesacrificial material, wherein after removing the top portion of thefirst material, an upper surface of a remaining portion of the firstmaterial is level with an upper surface of the remaining portion of thesacrificial material.